Studies will be carried out to synthesize depsipeptide lactone model compounds related to the depsipeptide portion of the quinoxaline antibiotics. The tridepsipeptide, N-carbobenzoxy-L-seryl-O-(N-t-butyloxycarbonyl-L-valyl)-L-alanine 4-(methylthio)phenyl ester has been prepared and will serve as a key intermediate in the preparation of related depsipeptide models. Following methods developed in the above model studies, efforts to affect the total synthesis of the quinoxaline antibiotic, triostin A, will be pursued. Studies also will be made to prepare beta, beta-dialkylmercapto amino acids, which comprise a structural moiety in the above antibiotics, via dehydroalanine derivatives as synthetic precursors. BIBLIOGRAPHIC REFERENCES: W. Chen and R.K. Olsen, "Synthesis of Di- and Tripeptides Containing 4-Aminocyclohexane carboxylic Acid" J. Org. Chem., 40, 350 (1975). W. Chen, M. Hsu, and R.K. Olsen, "Synthesis of a Model Depsipeptide Lactone Related to the Quinoxaline Antibiotics", J. Org. Chem., 40, 3110 (1975).